1. Technical Field
The present invention relates generally to data storage devices, and more specifically to methods and arrangements that can be employed to significantly reduce the processing requirements associated with the transfer of data from the storage device to an external device.
2. Background Art
An optical disc, such as, for example, a compact disc (CD) or digital versatile disc (DVD), is a nonmagnetic data storage medium on which relatively large amounts of digital information is stored by using a laser beam to burn microscopic indentations into a surface of the medium. The stored data is read using a lower-power laser to sense the presence or absence of the indentations.
There are many different types of optical disc systems (i.e., optical discs formats and devices) available today. One of the most common optical disc systems used in contemporary personal computers (PCs) is the compact disc read-only memory (CD-ROM). CD-ROM provides a read only optical storage medium onto which data is stored only once and then read many times using a CD-ROM drive. A CD-ROM disc can contain a mixed stream of digital image, audio, video, and/or text data Additional capacity is provided by a digital versatile disc read-only-memory (DVD-ROM). In the future, DVD-ROM will also be faster. Other advanced optical disc systems allow users to also write data to the optical disc. By way of example, a compact disc recordable (CD-R) system allows the user to write-once to each section of the optical disc, while a compact disc rewritable (CD-RW) allows the user to write to each section of the optical disc many times. Other notable optical disc systems include a compact disc magneto optical (CD-MO) disc, which is also rewritable.
Reading data from these exemplary optical disc systems typically begins with the PC's processor or host processor requesting that a block of data be scanned from the optical disc and transferred over a peripheral bus to the host processor or a primary memory. A block of data typically includes a plurality of smaller blocks or frames of data. These frames of data are typically pre-processed and logically gathered into groups within the optical disc drive, and then forwarded to the host processor over the peripheral bus. By way of example, an exemplary 16X CD-ROM drive for use with a PC typically includes a digital signal processing arrangement that pre-processes the retrieved data, and a buffer management arrangement that stores frames of data, which are typically between about 2 to about 3 kilobytes long, in a 128-kilobyte dynamic random access memory (DRAM) prior to transferring a group of frames to the host processor in a single burst.
One of the problems facing optical disc drive designers is that there can be different types of frames of data, depending upon the type/format of the optical disc, and, in certain situations, not all of these frames need to be transferred to the host processor.
For example, CD-ROM discs typically include data frames associated with certain "lead-in" and "lead-out" areas. These "lead area frames" contain a table of contents (TOC) descriptor that is used within the optical disc drive to properly locate and read the tracks recorded on the optical disc and to stay within permitted boundaries on the disc. In a further example, CD-R, CD-RW and other like recordable optical discs, typically employ a plurality of "link area frames", which are recorded between subsequently written blocks of data. These link area frames are also used within the optical disc drive to properly locate and read the blocks of data recorded on the track.
Consequently, it is preferred that the optical disc drive include the capability to determine which frames, within a block of data, are to be transferred to the host processor and which frames can be skipped or otherwise ignored and not transferred to the host processor. The task of determining which frames should be transferred to the host processor is typically conducted within a buffer manager arrangement, which can be configured to further process or otherwise examine each of the frames of data, for example, using a firmware-based processor that is responsive to a real-time firmware program. This frame-by-frame examination process tends to be burdensome on the buffer management arrangement, and at times other processing resources. Additionally, new generations of optical disc drives can introduce changes to the existing optical disc formats, or increase the speed at which an optical disc is read. As such, the processing capability of a conventional firmware-based processor may not be able to support the necessary processing demands and time constraints required in the future.
With this in mind, and considering that it is usually desirable for an optical disc drive to be compatible with the different optical disc formats/types, there is a need for methods and arrangements that effectively reduce the processing burden in an optical disc drive, and streamlines the transfer of frames from the optical disc drive to the host processor.